Evaluation of HOx sources and cycling using measurement-constrained model calculations in a 2-methyl-3-butene-2-ol (MBO) and monoterpene (MT) dominated ecosystem
Evaluation of HOx sources and cycling using measurement-constrained model calculations in a 2-methyl-3-butene-2-ol (MBO) and monoterpene (MT) dominated ecosystem
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DOI：
10.5194/acp-13-2031-2013
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发表时间：
2013-01-01
影响因子：
6.3
通讯作者：
Flocke, F. F.
中科院分区：
文献类型：
--
作者：
Kim, S.;Wolfe, G. M.;Flocke, F. F.
我们提出了一个详细的分析OH观测从BEACHON（能源，气溶胶，碳，H2O，有机物和氮的生物-水-大气相互作用）-ROCS（落基山有机碳研究）2010年实地活动在马尼图森林观测站（MFO），这是一个2-甲基-3-丁烯-2-醇（MBO）和单萜（MT）为主的森林环境。一套全面的测量被用来限制初级生产的OH通过臭氧光解，OH从HO 2回收，和OH的化学损失率，以估计稳态浓度的OH。此外，华盛顿大学化学模型（UWCM）被用来评估一个近明确的化学机制的性能。从稳态计算的OH的日循环是在良好的协议与测量。从HO 2 + NO反应的光解生产率和再循环率之间的比较表明，再循环率类似于20倍快于从臭氧的光解OH生产率。因此，我们发现，直接测量的回收率和OH损失率可以提供准确的预测OH浓度。更重要的是，我们还得出结论，传统的OH循环途径（HO 2 + NO）可以解释在这种非异戊二烯环境中观察到的OH水平。这与异戊二烯占主导地位的地区的观察结果相反，在那里，研究人员观察到OH的显着低估，并推测OH的来源不明。高度约束的UWCM计算低估了观测到的HO 2多达8倍。由于HO 2通过再循环为OH来保持氧化能力，UWCM低估了观察到的OH多达4倍。当UWCM计算受到测量的HO 2的约束时，模型计算的OH与观察到的OH水平更好地一致。相反，将模型约束到观测到的OH仅略微降低了模型测量的HO 2差异，这意味着未知的HO 2源。这些研究结果表明，限制输入的重要性，和内循环，ROx自由基池（OH + HO 2 + RO 2）。
We present a detailed analysis of OH observations from the BEACHON (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen)-ROCS (Rocky Mountain Organic Carbon Study) 2010 field campaign at the Manitou Forest Observatory (MFO), which is a 2-methyl-3-butene-2-ol (MBO) and monoterpene (MT) dominated forest environment. A comprehensive suite of measurements was used to constrain primary production of OH via ozone photolysis, OH recycling from HO2, and OH chemical loss rates, in order to estimate the steady-state concentration of OH. In addition, the University of Washington Chemical Model (UWCM) was used to evaluate the performance of a near-explicit chemical mechanism. The diurnal cycle in OH from the steady-state calculations is in good agreement with measurement. A comparison between the photolytic production rates and the recycling rates from the HO2 + NO reaction shows that recycling rates are similar to 20 times faster than the photolytic OH production rates from ozone. Thus, we find that direct measurement of the recycling rates and the OH loss rates can provide accurate predictions of OH concentrations. More importantly, we also conclude that a conventional OH recycling pathway (HO2 + NO) can explain the observed OH levels in this non-isoprene environment. This is in contrast to observations in isoprene-dominated regions, where investigators have observed significant underestimation of OH and have speculated that unknown sources of OH are responsible. The highly-constrained UWCM calculation under-predicts observed HO2 by as much as a factor of 8. As HO2 maintains oxidation capacity by recycling to OH, UWCM underestimates observed OH by as much as a factor of 4. When the UWCM calculation is constrained by measured HO2, model calculated OH is in better agreement with the observed OH levels. Conversely, constraining the model to observed OH only slightly reduces the model-measurement HO2 discrepancy, implying unknown HO2 sources. These findings demonstrate the importance of constraining the inputs to, and recycling within, the ROx radical pool (OH + HO2 + RO2).